My birthday is soon and I'm choosing thea new phone. My birthday is soon and I'm choosing a new phone.

My birthday is coming soon and I'm choosing thea new phone. My birthday is coming soon and I'm choosing a new phone.

“My birthday is soon” is also correct. You can also put a comma after “soon,” but that is not necessary.

But, I ran into a problem. But I ran into a problem.

Usually you do not need to put a comma after conjunctions.

I have already have chosen, that it will be samsung. I have already chosen that it will be samsung.

I have already have chosen,decided that it will sbe a Samsung. I have already decided that it will be a Samsung.

It is acceptable to put “I already have,” but it sounds more natural to have the “already” between “have” and the verb. The conjunction “that” does not need a comma before it. Usually, “choose” is not used to introduce a “that” clause. If company names are originally capitalized, they should always be capitalized. Here, “Samsung” is an adjective (“What kind of phone?”) being used as a noun (the “phone” in “Samsung phone” is implied) and you should use ”a” as an article. “I have already decided that it will be Samsung” is fine if you mean “I have already decided that the company will be Samsung” but I think your wording mostly implies “I have already decided that the phone will be a Samsung phone.” Other correct versions of this sentence: “I have already chosen to get a Samsung.” “I have already decided on a Samsung.” “I have already decided it will be a Samsung.”

So, I have chosen sSamsung. So, I have chosen Samsung.

(I am reading this as “I have chosen the company Samsung” as opposed to the above comments on the previous correction.)

I think the phone which isthat foldings is cool. I think the phone that folds is cool.

You use “which” when introducing information that is not necessary to the meaning of the sentence; if the information is necessary, you should use “that.” For example, in your sentence, the detail that the phone folds is necessary to describe the phone that is cool, so you should use “that.” “Is folding” is fine; I just prefer “folds.”

But I'm not sure how long thits phone screen will work. But I'm not sure how long its phone screen will work.

I decided between sSamsung fFlip3,s S22 and sS22+. I decided between Samsung Flip3, S22 and S22+.

This eEvery phones has advantages and disadvantages. Every phone has advantages and disadvantages.

This eEvery phones has advantages and disadvantages. Every phone has advantages and disadvantages.

It's so hard to think about it. It's so hard to think about.

I didn't think that my birthday willould be so hard. I didn't think that my birthday would be so hard.

I didn't think that my birthday willould be so hard. I didn't think that my birthday would be so hard.

Past tense of “think” plus a subordinate clause uses the conditional in the clause.